View Full Version : Radius cutter designs?

04-14-2007, 06:26 PM
I thought that I would throw this out there and see what comes back...

I am debating on which type of radius cutter to build, either yoke or turret style. Not having any experience with a radius cutter, I don't know what would be a better solution would be for the occasional need af amking a radius cut on the lathe.

So... What are the pros and cons of the different types of radius cutters that you have either made or bought?

04-14-2007, 09:30 PM
Here is the one I made. It's basically an adaption of Steve Bedair's design. Works well for me. I ended up mounting it to the base for my 4" vise.




04-14-2007, 10:20 PM
I got the kit for one from http://alisam.com/page/14g9f/Metalworking.html and I think it was about $25.00. It works fine. I'm now working on a kit from MLA
http://www.statecollegecentral.com/metallathe/MLA-7.html which is much more substantial. I'm using a South Bend 9A lathe.

Bob Parker

04-15-2007, 12:14 AM
This is one of the alternative designs. I don't have experience with others so I can't compare, but I can say this works. Easy swap to a quick change toolpost and back.


JC Hannum has one built around an offset boring head that he's posted pictures of.

Oops, sorry picture size is a little fat.

Peter N
04-15-2007, 03:40 AM
Here's my radius cutter.

It's adapted from the one designed by Holescreek on the PM forum for his Logan, but this one is to fit a Myford.
The cutter runs in a dovetail slide with a brass gib strip, radius adjustment is set via the knurled thumbwheel, and the whole thing pivots on a taper roller bearing.

I thought I should post a picture of it doing a concave cut, as everyone else seems to show their balls :D
The radius being cut is about 2.75".





04-15-2007, 08:29 AM
For some reason, I cannot post pictures just now. There are several different styles of radius fixtures in this thread, including a picture of mine.


The post type and up & over type may offer a bit more rigidity over the yoke style, but all serve their purposes. For the occasional one off ball of a fixed diameter, it is hard to beat the simplicity of Sir John's blunt file method.

Spin Doctor
04-15-2007, 08:43 AM
Having used both the yoke (Holdridge) ad turret types (Hardinge) in the "real world" IMO it depends on the size of the lathe and the work. In small machines the overall lack of rigidity in the bed and slides would IMO drive the solution towards the turret type. Once you get to a larger swing lathe, say 14" the yoke or Hodridge type really comes into its own. But the holdridge type has its own set of problems in terms of size control. versus the yoke types. Of course in the real world it is all a mote pont now with CNC.

04-15-2007, 11:48 AM
Here's my radius cutter.

It's adapted from the one designed by Holescreek on the PM forum for his Logan

Nice job Peter.

If anyone's interested in Holescreek's radius cutter, he has a very nice set of CAD drawings for it.

04-15-2007, 11:08 PM
I appreciate everyone's input! I have some food for thought now. To the drawing board.....

04-16-2007, 05:41 AM
OK ,it depends on the size of radii you want, for smaller ones I use a quarter round router bit, Simple easy and cheap.

04-16-2007, 06:41 AM
What is the trick to using one? Do you go whole hog in or do you gradually advance your cutter? Begin at the tailstock end or 90 degrees to the work? Thanks Fred

kap pullen
04-16-2007, 07:58 AM
Here is a tool made for forming the spherical bore in a golf ball mortar.

Sorry the photo isn't the greatest, but you can see the chips on the ways ok!


This design allows you to machine a bore with the centerline well below the face of the stock.

The bar in the front connects to the tailstock spindle for a positive feed.

Here is a store bought one with a worm, and gear for feed.



04-16-2007, 05:28 PM
Hey Kap, yours sounds very interesting. How does it work exactly?